Refrigerant feed control for centrifugal refrigeration machines

ABSTRACT

In a refrigeration system including a centrifugal compressor, a condenser, an economizer, and a cooler, there is provided control means to establish a full-flow passage between the condenser and the economizer for transmitting liquid and gaseous refrigerant to the economizer to raise the pressure therein above the pressure in the cooler existing at startup under certain conditions and during certain part load conditions, thereby permitting refrigerant liquid to flow in a normal fashion through the system.

United States Patent [72] Inventor William T. Osborne [56] ReferencesCited East Syracuse UNITED STATES PATENTS P 750 3,315,482 4/1967Kirtland 62/218 {22] Filed Jan. 5,1970

3,315,485 4/1967 Clark 62/218 Paemd 3 315 486 4/1967 LeChien 62/218 [73]Assignee Carrier Corp.

Syracuse, NY. Primary Examiner-Meyer Perlin Attorneys-Harry G. Martin,Jr. and J. Raymond Curtin REFRIGERANT FEED CONTROL FOR :SSTRACT: In arefrigeration system includciing a cintrifggal CENTRIFUGAL REFRIGERATIONMACHINES pre ssor, a condenser, an economrzer, an a coo er, t ere 4 cmIn 15 provided control means to establish a full-flow passage mungbetween the condenser and the eeonomizer for transmitting [S2] U.S. Cl62/197, liquid and gaseous refrigerant to the economizer to raise the62/218. 62/278, 62/510, 62/Dig. I7 pressure therein above the pressurein the cooler existing at [51] Int. Cl F25b 41/00 startup under certainconditions and during certain part load [50] Field of Search 62/196,conditions, thereby permitting refrigerant liquid to flow in a 197, 278,209. 218, 510 normal fashion through the system.

PATENTEll-Jlmzs |97l INVENTOR. WILLIAM T. OSBORNE ATTORNEY REFRIGERANTFEED CONTROL FOR CENTRIFUGAL REFRIGERATION MACHINES BACKGROUND OF THEINVENTION This invention has to do with refrigeration apparatusembodying a centrifugal compressor, a condenser, an economizer, and acooler. The compressor is equipped with the usual inlet guide vanes orthrottling means at the inlet of the compressor operable to control thecapacity of the machine.

Upon shutdown of apparatus of this type, the throttling means is movedto closed position. When the machine is started up, circumstances may be'such that difficulty will be experienced in getting the machine intocontinuous operation. For example, the condenser cooling water may be atan unusually low temperature due to the cooling tower being subjected toa low ambient temperature. On the other hand, the chilled water in theair conditioning system may, on startup, be at a high temperature. Underthese conditions, upon star tup of the machine, the pressure in thecooler will exceed the pressure in the economizer with the result thatthere will be no refrigerant flow from the economizer to the cooler, andany refrigerant in the cooler is quickly boiled off, whereby the coolerboils dry and the unit cuts out due to excessively low suction pressure.This action may take place quickly following startup of the machine andwithin the time lag established for the opening of the guide vanes atthe inlet of the compressor. This situation may also prevail at low orpart load operation withlow condensing water temperature.

This problem is to some extent solved by providing a buttertly valve ordamper in the gas line extending from the economizer to the inlet of thesecond compressor stage. That valve is rigged to be modulated to closedposition when a predetermined minimum pressure differential existsbetween the economizer and the evaporator. However, valves of thatnature are expensive; they tend to be unreliable; and they are notreadily serviceable.

SUMMARY OF THE INVENTION A pressure differential actuator is connectedto the economizer and the cooler. When the pressure in the coolerapproaches or exceeds the pressure in the economizer, this ac tuatoreffects operation of a switch connected to the float operated meteringrefrigerant valve for driving the valve to full open position regardlessof the float actuator associated with the valve.

BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a schematicrepresentation of refrigeration apparatus embodying my invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the FIGURE, theapparatus includes a condenser llO connected by line 11 to an economizer12. The economizer is connected by refrigerant line 13 to the cooler 14.The vapor space of the cooler 14 is connected by line 15 to the inletside of the centrifugal compressor 16, the output of which is connectedby line 21 to the condenser 10.

A metering valve 24 having an actuator 25 is operated by a v float 27 inthe condenser. The valve 24 and float 27 serve to maintain a liquid sealbetween the condenser and economizer as is conventional to prevent thepassage of gaseous refrigerant through line 11 to the economizer.

The vapor space in the economizer 12 is connected by a line 31 to anintermediate pressure area of the compressor. As is well understood, theline 31 may be connected to the housing enclosing the motor operatingthe compressor to provide refrigerant for cooling the motor with areturn line to the cooler 14. Also, if the compressor is a singlc-stagemachine, the line 31 may be connected to the gas flow passageintermediate the intake end of the impeller and the periphery thereof.In the form of the invention illustrated, the compressor is of thetwo-stage type having first and second stage impellers 33,34, the line31 being connected to the flow passage intermediate the impellerswhereby suction is provided by the second impeller 34 for reducing thepressure in the economizer 12 to effect partial evaporation of therefrigerant therein to the end of lowering the temperature thereof as iswell understood in the art. The compressor is provided at the intakewith throttling means as guide vanes 35.

At startup of the machine with the throttling means 35 closed, or withthe throttling means closed at low or part load operation and with theeconomizer exposed to the inlet pressure at the intermediate pressurestage of the compressor, the economizer pressure will drop below thecooler pressure. This is particularly true if the machine is started upwith warm chilled water in the tube bundle 37 of the cooler 14 and,also, with the presence of low temperature water in the condenser coil39. Under these conditions, the pressure in the cooler 14 may wellexceed the pressure in the economizer 12, with the result that norefrigerant can flow through line 13 to the cooler 14.

In normal operation, the guide vanes 35 are under the control of atemperature sensor associated with the output line of the tube bundle37; and upon elevation of the temperature of the water in that line, theguide vanes are moved to open position to establish the full capacity ofthe machine. However, particularly at startup, there is a programmedtime lag in the operation of the vanes 35. With no flow of refrigerantfrom the economizer to the cooler, any refrigerant remaining in thecooler is quickly vaporized under the: conditions stated, with theresult that the cooler boils dry and the unit cuts out from excessivelylow suction pressure.

By my invention, there is provided control means operable upon thepressure in the economizer becoming equal to or less than the pressurein the cooler 14 to provide a full-flow passage from the condenser 10 tothe economizer 12. This full flow passage may be established byproviding the valve 24 with an override actuator in the form of solenoid45 which, when energized, will operate the valve 24 to full openposition regardless of the position of the float .27. The overrideactuator 45 is connected by a line 46 to a switch 47. The switch 47 isoperated by a pressure differential means 48 connected in a line 49extending from the vapor area of the economizer 12 to the vapor area ofthe cooler 14. The pressure differential device 48 functions to energizethe override actuator 45 of valve 24 when the pressure in the coolerapproaches or exceeds that in the economizer, in which event the valve24 is operated to full open position permitting liquid and gaseousrefrigerant to pass into the economizer 12. Due to the impedance in line31 and the restriction and choking effect of opening 50, the pressure inthe economizer is raised above the pressure then existing in the cooler14, whereby the refrigerant in the economizer l2 flows to the cooler 14.

Iclaim:

l. Refrigeration apparatus comprising a compressor, a con denser, aneconomizer, and a cooler, a line extending from said condenser to saideconomizer, metering valve means in said line operable to meter the flowof liquid refrigerant from said condenser to said economizer, a lineconnecting said economizer to said cooler, and control means operableupon the pressure in said cooler approaching the pressure in saideconomizer to provide an open flow passage for transmission ofrefrigerant gas from said condenser to said economizer.

2. Refrigeration apparatus as set forth in claim 1 wherein said controlmeans is operable independently of said metering valve means.

3. Refrigeration apparatus as set forth in claim 1 wherein said controlmeans includes an override actuator operable upon the pressure in saidcooler approaching the pressure in said economizer to move said meteringvalve to open position.

4. Refrigeration apparatus as set forth in claim 1 wherein said meteringvalve means consists of a float-operated valve, said control meansincludes a solenoid connected to said valve tuating means operable uponthe pressure in said cooler approaching the pressure in said economizerto actuate said switch to energize said circuit.

1. Refrigeration apparatus comprising a compressor, a condenser, aneconomizer, and a cooler, a line extending from said condenser to saideconomizer, metering valve means in said linE operable to meter the flowof liquid refrigerant from said condenser to said economizer, a lineconnecting said economizer to said cooler, and control means operableupon the pressure in said cooler approaching the pressure in saideconomizer to provide an open flow passage for transmission ofrefrigerant gas from said condenser to said economizer.
 2. Refrigerationapparatus as set forth in claim 1 wherein said control means is operableindependently of said metering valve means.
 3. Refrigeration apparatusas set forth in claim 1 wherein said control means includes an overrideactuator operable upon the pressure in said cooler approaching thepressure in said economizer to move said metering valve to openposition.
 4. Refrigeration apparatus as set forth in claim 1 whereinsaid metering valve means consists of a float-operated valve, saidcontrol means includes a solenoid connected to said valve and operableupon energization to move said valve to open position independently ofsaid float, an energizing circuit for said solenoid including a normallyopen switch and switch actuating means operable upon the pressure insaid cooler approaching the pressure in said economizer to actuate saidswitch to energize said circuit.